The invention relates generally to the chemical vapor deposition (CVD) of platinum group metals on an integrated circuit structure as a continuous film and with good step coverage. The invention also relates to integrated circuits having a platinum group metal layer, used, for example, as the lower electrode in a capacitor.
Because of their high corrosion resistance, microelectronic devices having platinum group metals are desired in applications where great reliability is desired and also where a corrosive atmosphere may be present. A process is needed to deposit a platinum group metal having good step coverage and where the platinum film can be patterned to avoid an extra etching step.
Conventional methods of depositing platinum films suffer drawbacks in that these methods are unable to consistently create a continuous uniformly thin platinum film that additionally has good step coverage. These conventional prior methods include vacuum deposition methods, sputtering methods and even chemical vapor deposition. Even in the conventional chemical vapor deposition methods it is difficult to create a continuous uniform platinum film with good step coverage.
This is likely due to the fact that when conventional platinum precursors are used in the conventional chemical vapor deposition methods, it is difficult to control the nucleation rate of the platinum films. At the outset of the platinum deposition process, the nucleation rate of the platinum film onto the surface of the substrate is very slow; however, once nucleation does begin the deposition rate of the platinum film onto the surface increases significantly. In fact, it is difficult to control or even slow the rate of deposition once the conventional methods begin depositing platinum onto the surface of the substrate. In the conventional methods therefore, it is difficult to begin the deposition process and even more difficult to thereafter control the deposition rate so as to arrive at a uniform thin platinum film having good step coverage.
One example of the problem with using conventional methods to deposit platinum is discussed with reference to FIG. 1. Here it is desired to deposit a platinum layer 210 onto the side surfaces of a deep container capacitor 230. The platinum layer 210 is formed by CVD deposition using a conventional platinum precursor. As the process begins, a platinum film 210 forms on the upper layer 220 of the capacitor 200. Since it is difficult to control the deposition rate of the platinum layer 210, the platinum layer 210 quickly forms a thick layer on the upper layer 220 of the capacitor 230 before it can coat the inside walls of the capacitor 230. That is, the quickly formed platinum layer 210 pinches together over the opening 230 in the capacitor 200 and very little platinum is able to form on the inside walls 240 or the bottom 250 of the capacitor 230. Thus, an inconsistent platinum film is formed on the inside walls 240 and the bottom 250 of the capacitor 230 without good step coverage.
One prior solution to increase the smoothness of the film deposited was to increase the temperature at which the metal is deposited. When the temperature at which the conventional CVD process operates is increased, the growth rate of the platinum also increases. While increasing the temperature does result in a smoother film, the increased temperature also increases the deposition rate and the pinch-off effect, as previously described. If the temperature of the CVD process is decreased, the growth rate of the platinum also decreases, resulting in better step coverage; however, when the temperature of the CVD process is decreased the carbon content of the deposited film increases, resulting in poor film quality.
To reduce the carbon content of the film, the conventional methods added oxygen during the CVD process. The oxygen removed some of the carbon from the platinum film; however, the oxygen also increased the deposition rate of the platinum resulting in a film similar to the high temperature deposited film described above. Thus, with conventional methods it is difficult to achieve both good step coverage and a smooth continuous film, which is especially important in the manufacture of an integrated circuit. Additionally, conventional methods often require that the platinum film be etched to remove the deposited platinum film where it is not desired.
The present invention overcomes the drawbacks of patterning platinum group metals by conventional methods and provides a CVD method which produces a smooth, uniform, continuous film of a platinum group metal which also has good step coverage. The present invention also allows the platinum film to be patterned onto a substrate. The invention includes depositing the platinum metal group in conjunction with ultraviolet light using a CVD process followed by low temperature annealing in order to remove carbon in the platinum group metal.
The invention relates to the formation of a continuous film layer of platinum group metal by CVD. The invention may find many uses where a thin uniform layer of platinum group metal is needed. For example, the invention is useful in the computer microchip industry, such as for the undercoating electrode of a dielectric memory in a semiconductor device. The invention relates to a chemical vapor deposition method to deposit the platinum group metal onto a surface. The starting material for preparation of the platinum group metal film may be any organic platinum group metal precursor suitable for deposition of the platinum group metal.
The invention provides a process for depositing a platinum metal on a substrate which includes the steps of flowing a gas having adsorbed therein a predetermined thickness of platinum metal precursor over the substrate at a selected temperature and pressure in the presence of ultraviolet light or flowing the platinum metal precursor over a substrate and then irradiating the substrate with ultraviolet light. The selected operating temperature is a temperature at which the platinum group metal deposits on the substrate, but less than a temperature at which the platinum group metal fails to smoothly deposit on the substrate. The pressure at which the process operates is a pressure at which the platinum group metal will deposit on the substrate in a continuous film while maintaining good step coverage. The substrate is a non-silicon containing film. In order to avoid silicidation of platinum during anneal, the substrate is then subjected to a low temperature anneal in the presence of oxygen at a temperature low enough as to not oxidize the substrate. By carrying out this process, a platinum group metal film may be deposited on the exposed portions of the substrate in a uniform film.
The above and other advantages and features of the invention will be more clearly understood from the following detailed description which is provided in connection with the accompanying drawings.